1. Field of the Invention
The present invention relates generally to Integrated Circuit (IC) devices, and more particularly, to a multi-layer Printed Circuit Board (PCB) having an IC package built therein and a method for fabricating the PCB.
2. Description of the Related Art
In order to satisfy increasing demands for smaller-sized, slim electronic devices and their various additional functions, high integration technology is essential. A conventional PCT has Surface Mount Device (SMD) components. However, techniques have been proposed, in which components are built within a PCB, allowing for the integration of more components.
One such technique builds an IC in a PCB by re-wiring the IC in a Wafer Level Package (WLP). The PCB with the built-in IC package provides sophisticated functionality along with miniaturization and function diversity. Thus, the PCB minimizes a wiring distance for a high frequency of 100 MHz or higher, and in some cases overcomes a reliability problem encountered through connections produced by wire bonding or a solder ball as used for a Flexible Circuit Board (FCB) or a Ball Grid Array (BGA).
FIGS. 1 to 3B illustrate structures of conventional PCBs each having one or more built-in IC packages.
FIG. 1 is a schematic view illustrating a structure of the conventional PCB with a built-in IC package. A multi-layer PCB includes a core layer 110 having a core insulation layer 111 and core conductive layers 112 and 113. The multi-layer PCB also includes build-up layers 120 and 130 in which insulation layers 121 and 131 and conductive layers 122 and 132 are alternately deposited. Via holes 123 and 133 are formed into the insulation layers 121 and 131 for an electrical connection between layers and to the outside. A WLP 150 is provided with a plurality of conductive bumps 152 on a top surface of an IC 151 for external electrical connection. The WLP 150 is accommodated within a cavity 150A formed into the core insulation layer 111 of the multi-layer PCB. The WLP 150 has a die attach film 160 attached onto a surface of the IC 151 that does not have the conductive bumps 152. The die attach film 160 is also attached to the bottom of the cavity, specifically, to the core conductive layer 113 under the core insulation layer 111.
Conventionally, a fan-out operation connects the built-in IC package to the outside through the formation of a cavity by peeling off the copper foil of a core conductive layer and performing wiring via holes formed by applying a laser beam to a layer built up on the core layer. Therefore, at least one build-up layer is required for the fan-out operation. When there are a large number of interconnections with the outside, a plurality of build-up layers are needed, thereby increasing the cost of the PCB.
Moreover, when a plurality of IC packages are arranged on the PCB, two or more IC packages 150 are usually built in one direction in the conventional technology, as illustrated in FIGS. 2A and 2B. Thus it is difficult to change the built-in directions of the IC packages to be different from each other.
When two IC packages are built in opposite directions as illustrated in FIG. 3A, the same process is repeated and both surfaces of the core layer 110 may not be utilized. As a result, more build-up layers 120, 120′, 130 and 130′ are used as illustrated in FIG. 3B, thereby increasing the cost.